U.S. patent number 10,456,597 [Application Number 15/547,359] was granted by the patent office on 2019-10-29 for multileaf collimator and radiation treatment device.
This patent grant is currently assigned to Hitachi, Ltd.. The grantee listed for this patent is Hitachi, Ltd.. Invention is credited to Satoshi Arai, Akihiro Miyamoto.
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United States Patent |
10,456,597 |
Arai , et al. |
October 29, 2019 |
Multileaf collimator and radiation treatment device
Abstract
This multileaf collimator is provided with multiple leaves which
limit the area irradiated by a radiation beam and which are
arranged in the thickness direction. Each of the leaves is provided
with a protruded portion which is formed protruding towards a first
surface of the leaf, a depressed portion which is formed in the
second surface of the leaf and into which the protruded portion
formed on another leaf is inserted, a first curved surface which is
formed between the first surface of the leaf and the lateral
surface of the protruded portion, and a second curved surface which
is formed between the second surface of the leaf and the lateral
surface of the depressed portion.
Inventors: |
Arai; Satoshi (Tokyo,
JP), Miyamoto; Akihiro (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi, Ltd. |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
56542703 |
Appl.
No.: |
15/547,359 |
Filed: |
January 29, 2015 |
PCT
Filed: |
January 29, 2015 |
PCT No.: |
PCT/JP2015/052528 |
371(c)(1),(2),(4) Date: |
July 28, 2017 |
PCT
Pub. No.: |
WO2016/121051 |
PCT
Pub. Date: |
August 04, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180021596 A1 |
Jan 25, 2018 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N
5/1045 (20130101); A61N 5/1077 (20130101); A61N
5/10 (20130101) |
Current International
Class: |
A61N
5/10 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
0259989 |
|
Mar 1988 |
|
EP |
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2003-210595 |
|
Jul 2003 |
|
JP |
|
2008-068092 |
|
Mar 2008 |
|
JP |
|
2009-034443 |
|
Feb 2009 |
|
JP |
|
2009-160055 |
|
Jul 2009 |
|
JP |
|
4436340 |
|
Mar 2010 |
|
JP |
|
Other References
Extended European Search Report for application No. 15879948.6,
dated Oct. 4, 2018, 7 pages. cited by applicant .
International Search Report received for PCT Patent Application No.
PCT/JP2015/052528 dated Apr. 28, 2015, 7 pages. cited by
applicant.
|
Primary Examiner: Maupin; Hugh
Claims
The invention claimed is:
1. A multileaf collimator for regulating a range irradiated with a
radiation beam, comprising: a plurality of leaves arranged along a
thickness direction, wherein each of the plurality of leaves
comprising; a protruded portion protrudingly formed on a first side
surface in a plate thickness direction of the leaf, a depressed
portion formed in a second side surface in the plate thickness
direction of the leaf, and configured to receive insertion of the
protruded portion formed on another one of the plurality of leaves,
a first curved surface formed between the first side surface of the
leaf and a lateral surface of the protruded portion, and a second
curved surface formed between the second side surface of the leaf
and a lateral surface of the depressed portion.
2. The multileaf collimator according to claim 1, wherein: when a
gap g1 between two leaves, among the plurality of leaves, the two
leaves being positioned side by side in the thickness direction,
and a gap g2 between the lateral surface of the depressed portion
in a first one of the two leaves and the lateral surface of the
protruded portion in a second one of the two leaves satisfy a
relationship of: g1<g2, a radius R of curvature of the first
curved surface and the second curved surface satisfies a
relationship of: R.ltoreq.g1.
3. The multileaf collimator according to claim 1, wherein: when a
gap g1 between two leaves, among the plurality of leaves, the two
leaves being positioned side by side in the thickness direction,
and a gap g2 between the lateral surface of the depressed portion
in a first one of the two leaves and the lateral surface of the
protruded portion in a second one of the two leaves satisfy a
relationship of: g2.ltoreq.g1, a radius R of curvature of the first
curved surface and the second curved surface satisfies a
relationship of: R.ltoreq.g2.
4. The multileaf collimator according to claim 1, wherein: when a
gap g1 between two leaves, among the plurality of leaves, the two
leaves being positioned side by side in the thickness direction and
a gap g2 between the lateral surface of the depressed portion in a
first one of the two leaves and the lateral surface of the
protruded portion in a second one of the two leaves satisfy a
relationship of: g1.ltoreq.g2, a radius R of curvature of the first
curved surface and the second curved surface satisfies a
relationship of: g1.ltoreq.R.ltoreq.g2.
5. The multileaf collimator according to claim 1, wherein when a
gap g1 between two leaves, among the plurality of leaves, the two
leaves being positioned side by side in the thickness direction and
a gap g2 between the lateral surface of the depressed portion in a
first one of the two leaves and the lateral surface of the
protruded portion in a second one of the two leaves satisfy a
relationship of: g2.ltoreq.g1, a radius R of curvature of the first
curved surface and the second curved surface satisfies a
relationship of: g2.ltoreq.R.ltoreq.g1.
6. A radiation treatment apparatus, comprising: the multileaf
collimator according to claim 1, and a radiation beam irradiation
device that irradiates the multileaf collimator with the radiation
beam.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a national phase claiming the benefit of and
priority to International Patent Application No. PCT/JP2015/052528,
entitled "MULTILEAF COLLIMATOR AND RADIATION TREATMENT DEVICE"
filed Jan. 29, 2015, which is hereby incorporated by reference in
its entirety.
TECHNICAL FIELD
The present invention relates to a multileaf collimator for
regulating a field irradiated by a radiation beam to conduct a
radiation treatment, and to a radiation treatment apparatus using
the multileaf collimator.
BACKGROUND
Tumor treatment methods include, as one method for treating a
tumor, radiation treatments of irradiating an affected site with a
radiation beam. In the radiation treatments, it is desirable to
effectively irradiate the affected site with the radiation beam
while minimizing an irradiated dose of the radiation beam (a dose)
applied to a patient.
To achieve this, there have been used multileaf collimators for
regulating a field of irradiation which is a radiation region/a
radiation shape of a radiation beam.
Such a multileaf collimator includes a plurality of leaves in the
shape of thin plates. The leaves are, in a frame, arranged side by
side and spaced from each other along a plate thickness direction
of the leaves. Further, each of the leaves is configured to be
independently movable by means of a drive mechanism, and therefore
allowed to be individually advanced into or retreated from the
radiation region of the radiation beam. When the leaves are
positioned in the radiation region, the radiation beam is screened
by the leaves, to thereby regulate the field of irradiation. That
is, regulating the field of irradiation can achieve formation of a
field irradiated with the radiation beam adjusted for each
patient.
In the multileaf collimator, it is necessary that the radiation
beam should be prevented from leaking through a gap between leaves
adjacent to each other. Patent Literature 1 discloses a structure
in which a protrusion is provided to a first surface of a leaf and
a groove is provided to a second surface of the leaf. In this
structure, the protrusion on a first one of mutually adjacent
leaves is inserted into the groove in a second one of the mutually
adjacent leaves. This structure can function to prevent leakage of
the radiation beam through a space between the mutually adjacent
leaves.
CITATION LIST
Patent Literature
Patent Literature 1: Japan Patent No. 4,436,340 B
SUMMARY
Technical Problem
In radiation treatment apparatuses, it has been desired to further
improve resolutions of the apparatuses. In order to enhance a
resolution, the thickness of leaves in a multileaf collimator
should be minimized.
However, when the leaves are reduced in thickness, such a thinned
leaf tends to be easily cracked or broken due to stress
concentrated in stepped regions (corner parts) provided to form a
protrusion and a groove in the leaf.
An object of the present invention is to provide a multileaf
collimator whose resolution is enhanced while minimizing leakage of
a radiation beam and preventing occurrence of a crack or breakage
of a leaf, and provide a radiation treatment apparatus.
Solution to Problem
According to a first aspect of the present invention, there is
provided a multileaf collimator for regulating a range irradiated
by a radiation beam. The multileaf collimator is equipped with a
plurality of leaves arranged along the thickness direction. Each of
the leaves includes a protruded portion protrudingly formed on a
first side surface of the leaf and a depressed portion formed in a
second side surface of the leaf and configured to receive insertion
of the protruded portion formed in another one of the leaves. Each
of the leaves further includes a first curved surface formed
between the first side surface in a plate thickness direction of
the leaf and a lateral surface of the protruded portion, and a
second curved surface formed between the second side surface in the
plate thickness direction of the leaf and a lateral surface of the
depressed portion.
According to a second aspect of the present invention, in the
multileaf collimator according to the first aspect, when a gap g1
between two leaves, among the plurality of leaves, arranged side by
side in the thickness direction, and a gap g2 between the lateral
surface of the depressed portion in a first one of the two leaves
and the lateral surface of the protruded portion in a second one of
the two leaves satisfy a relationship of g1.ltoreq.g2, a radius R
of curvature of the first curved surface and the second curved
surface may be defined to satisfy a relationship of
R.ltoreq.g1.
According to a third aspect of the present invention, in the
multileaf collimator according to the first aspect, when a gap g1
between two leaves, among the plurality of leaves, arranged side by
side in the thickness direction and a gap g2 between the lateral
surface of the depressed portion in a first one of the two leaves
and the lateral surface of the protruded portion in a second one of
the two leaves satisfy a relationship of g2.ltoreq.g1, a radius R
of curvature of the first curved surface and the second curved
surface may be defined to satisfy a relationship of
R.ltoreq.g2.
According to a fourth aspect of the present invention, in the
multileaf collimator according to the first aspect, when a gap g1
between two leaves, among the plurality of leaves, arranged side by
side in the thickness direction and a gap g2 between the lateral
surface of the depressed portion in a first one of the two leaves
and the lateral surface of the protruded portion in a second one of
the two leaves meet a relationship of g1.ltoreq.g2, a radius R of
curvature of the first curved surface and the second curved surface
may be defined to satisfy a relationship of
g1.ltoreq.R.ltoreq.g2.
According to a fifth aspect of the present invention, the multileaf
collimator according to the first aspect, when a gap g1 between two
leaves, among the plurality of leaves, arranged side by side in the
thickness direction and a gap g2 between the lateral surface of the
depressed portion in a first one of the two leaves and the lateral
surface of the protruded portion in a second one of the two leaves
satisfy a relationship of g2.ltoreq.g1, a radius R of curvature of
the first curved surface and the second curved surface may be
defined to satisfy a relationship of g2.ltoreq.R.ltoreq.g1.
According to a sixth aspect of the present invention, there is
provided a radiation treatment apparatus that includes the
multileaf collimator according to any one of the first to fifth
aspects and a radiation beam irradiation device that irradiates the
multileaf collimator with a radiation beam.
Advantageous Effects of Invention
According to the above-described multileaf collimator and the
radiation treatment apparatus, leakage of a radiation beam can be
minimized while preventing occurrence of a crack or breakage in the
leaves.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 A diagram showing a functional configuration of a radiation
treatment system in an embodiment of this invention.
FIG. 2 A perspective view showing a schematic configuration of a
radiation treatment apparatus which is a component of the radiation
treatment system in the embodiment of this invention.
FIG. 3 A cross sectional view showing a radiation beam irradiation
device in the embodiment of this invention.
FIG. 4 A perspective view showing an outer appearance of a
multileaf collimator constituting a part of the radiation beam
irradiation device in the embodiment of this invention.
FIG. 5 A cross sectional view of the multileaf collimator in the
embodiment of this invention taken along a width direction.
FIG. 6 A cross sectional view of the multileaf collimator in the
embodiment of this invention taken along a direction perpendicular
to a plate thickness direction of leaves.
FIG. 7 A perspective view showing the leaves and a drive device for
driving the leaves in the embodiment of this invention.
FIG. 8 A perspective view showing a configuration of the drive
device in the embodiment of this invention.
FIG. 9 A diagram showing the shape of the leaves in the embodiment
of this invention.
FIG. 10 An enlarged view showing regions opposed to each other in
two leaves within a leaf group in the embodiment of this
invention.
FIG. 11 A diagram showing a modification example of the embodiment
of this invention in an exposed view.
DESCRIPTION OF EMBODIMENTS
FIG. 1 is a diagram showing a functional configuration of a
radiation treatment system 10 in an embodiment of this
invention.
As shown in FIG. 1, the radiation treatment system 10 includes a
treatment planning apparatus 11, a controller (a control unit) 12,
and a radiation treatment apparatus 20.
The treatment planning apparatus 11 is an apparatus for receiving
external inputs of properties of a radiation beam to be irradiated
onto a patient (such as the intensity, a time period, an angle, a
position, and a radiation region of the radiation beam to be
irradiated onto the patient), and the properties are previously
specified in accordance with details of a radiation treatment
administered to the patient. The treatment planning apparatus 11
outputs various parameter values for control operation performed to
radiate a radiation beam corresponding to the input properties of
the radiation beam.
The controller 12 controls operation of the radiation treatment
apparatus 20 based on the various parameter values generated in the
treatment planning apparatus 11. The controller 12 is a computer
device, such as a personal computer, that performs processing based
on a predetermined program. The controller 12 is connected to the
radiation treatment apparatus 20 through a wireless or wired
communication line to enable bidirectional transmission of
information.
FIG. 2 is a perspective view showing a schematic configuration of
the radiation treatment apparatus 20 which is a component of the
radiation treatment system 10.
As shown in FIG. 2, the radiation treatment apparatus 20 is
equipped with a ring frame 21, a traveling gantry 22, and a
radiation beam irradiation device 24.
The ring frame 21 is formed in the shape of a cylinder which is
circular in cross section. The ring frame 21 is disposed with a
center axis C1 substantially aligned with a horizontal direction.
In the ring frame 21, a rotating shaft 25 extending downward is
integrally formed on an outer circumferential surface of the ring
frame 21 at a lower end part 21a thereof. The rotating shaft 25 is
supported by a base (not illustrated in the diagram) in a condition
capable of rotating around a center axis C2 of the rotating shaft
25. The rotating shaft 25 is rotatably driven by a rotation drive
mechanism (not illustrated). That is, the ring frame 21 is rotated
about a vertical axis in conjunction with the rotating shaft 25
that is rotated by the rotation drive mechanism.
The traveling gantry 22 is formed in the shape of a cylinder which
is circular in cross section. The traveling gantry 22 is arranged
on an inner circumference side of the ring frame 21. The traveling
gantry 22 is supported by the ring frame 21 and configured to be
rotatable along an inner circumferential surface of the ring frame
21. In other words, the traveling gantry 22 shaped like a ring is
able to rotate about the center axis C1 extending along the
horizontal direction. The traveling gantry 22 is rotatably moved
along a circumferential direction by a gantry drive mechanism (not
shown).
The radiation beam irradiation device 24 emits a medical radiation
beam Sr under control of the controller 12 (see FIG. 1). The
radiation beam irradiation device 24 is supported on an inner
circumferential surface 22a of the traveling gantry 22. The medical
radiation beam Sr emitted from the radiation beam irradiation
device 24 is adjusted so as to pass through an isocenter C0 which
is an intersection point of the center axis C2 around which
rotational movement of the ring frame 21 occurs and the center axis
C1 around which rotational movement of the traveling gantry 22
occurs.
When the radiation beam irradiation device 24 is supported by the
traveling gantry 22 as described above, the medical radiation beam
Sr is always emitted so as to pass through the isocenter C0
irrespective of rotational movement of the ring frame 21 about the
center axis C2 and rotational movement of the traveling gantry 22
about the center axis C1.
The radiation treatment apparatus 20 is further equipped with a
sensor array 23. The sensor array 23 receives the medical radiation
beam Sr, which has, after having been emitted from the radiation
beam irradiation device 24, passed through an object existing in
the vicinity of the isocenter C0, and generates a transmission
image of the object. As the sensor array 23, an FPD (Flat Panel
Detector), an X-ray II (Image Intensifier), or the like may be
used.
Further, the radiation treatment apparatus 20 includes diagnostic
X-ray sources 26A and 26B and sensor arrays 27A and 27B.
The diagnostic X-ray sources 26A and 26B are mounted in an inner
circumferential side of the traveling gantry 22. The diagnostic
X-ray sources 26A and 26B are arranged on both sides of the ring
frame 21 in a circumferential direction across the center of the
radiation treatment apparatus 20 (i.e. the center axis C2 of
rotational movement of the ring frame 21). The diagnostic X-ray
sources 26A and 26B are controlled by the controller 12 to emit a
diagnostic X-ray 101 toward the isocenter C0. The diagnostic X-ray
101 is a circular cone beam which is conically spread from a point
owned by each of the diagnostic X-ray sources 26A and 26B.
The sensor arrays 27A and 27B are supported on the inner
circumferential surface 22a of the traveling gantry 22. The sensor
arrays 27A and 27B are arranged so as to be opposed to the
diagnostic X-ray sources 26A and 26B across the isocenter C0. The
sensor arrays 27A and 27B receive the diagnostic X-ray 101, which
has, after having been emitted from the diagnostic X-ray sources
26A and 26B, passed through the object existing in the vicinity of
the isocenter C0, and generate transmission images of the object.
As the sensor arrays 27A and 27B, for example, an FPD (Flat Panel
Detector), an X-ray II (Image Intensifier), or the like may be
used.
The radiation treatment apparatus 20 further includes a couch 28
and a couch actuator 29. The couch 28 has an upper surface 28a on
which a patient B to be treated by the radiation treatment system
10 lies down horizontally.
The couch actuator 29 is controlled by the controller 12 to move
the couch 28. The couch actuator 29 is supported by a base (not
illustrated).
FIG. 3 is a cross sectional view showing the radiation beam
irradiation device 24 which is a component of the radiation
treatment apparatus 20.
As shown in FIG. 3, the radiation beam irradiation device 24
includes an electron beam accelerator 51, an X-ray target 52, a
primary collimator 53, a flattening filter 54, a secondary
collimator 55, and a multileaf collimator 60.
The electron beam accelerator 51 irradiates the X-ray target 52
with an electron beam S0 generated by accelerating electrons.
The X-ray target 52 is formed of tungsten, a tungsten alloy, or
other similar materials. The X-ray target 52 irradiated with the
electron beam S0 emits a radiation beam S1.
The primary collimator 53 blocks a part of the radiation beam S1 to
prevent regions other than a desired site from being irradiated
with the radiation beam S1. The primary collimator 53 has a through
hole 53h into with the radiation beam S1 emitted from the X-ray
target 52 is directed to pass through. The primary collimator 53 is
formed of lead, tungsten, or the like.
The flattening filter 54 is a filter that functions to
substantially uniformly spread a dose of the radiation beam S1 on a
plane perpendicular to a radiation direction of the radiation beam
S1. The flattening filter 54 is formed of aluminum or the like. The
flattening filter 54 is mounted on an exit side of the through hole
53h in the primary collimator 53. The flattening filter 54 has a
substantially conical protrusion 54a oriented to point an X-ray
target 52 side. The shape of the protrusion 54a is designed to make
the dose of the radiation bean S1 spread substantially uniformly on
the plane perpendicular to the radiation direction of the radiation
beam S1.
The secondary collimator 55 blocks a part of the radiation beam S1.
The secondary collimator 55 has, in its center region, a through
hole 55h. The secondary collimator 55 allows a radiation beam S2 to
pass only through the through hole 55h. The secondary collimator 55
is formed of lead, tungsten, or the like.
The radiation beam S2 whose intensity distribution is made uniform
after passing through the primary collimator 53, the flattening
filter 54, and the secondary collimator 55 described above is
further blocked partially by the multileaf collimator 60. The
multileaf collimator 60 is controlled by the controller 12 to
regulate a field irradiated with the radiation beam S2. The
multileaf collimator 60 generates the medical radiation beam Sr
corresponding to the properties of the radiation beam to be
irradiated onto the patient.
FIG. 4 is a perspective view showing an outside appearance of the
multileaf collimator 60 constituting a part of the radiation beam
irradiation device 24. FIG. 5 is a cross sectional view of the
multileaf collimator 60 taken along a width direction. FIG. 6 is a
cross sectional view of the multileaf collimator 60 taken along a
direction perpendicular to a second direction which is a direction
along the thickness of a leaf 70 (hereinafter referred to as a
plate thickness direction T).
As shown in FIGS. 4 to 6, the multileaf collimator 60 includes a
frame 61, a plurality of leaves 70, and a drive device (driving
mechanism) 90.
The frame 61 is formed in the shape of a rectangular box having
longitudinal sides along one direction. The frame 61 is arranged in
such a manner that a first direction (hereinafter referred to as a
width direction W), which is a longitudinal direction of the frame
61, is orthogonal to a radiation beam irradiation axis of the
radiation beam irradiation device 24. In the frame 61, a leaf
housing part 62 is formed so as to be continuously hollow in the
width direction W.
In the frame 61, openings 63, which penetrate outer peripheral
sides of the frame 61 through the leaf housing part 62, are formed
in both an upper surface part 61a located on a side of the frame 61
opposed to the radiation beam irradiation device 24 and a lower
surface part 61b located on the other side from the upper surface
part 61a (in FIG. 4, only one of the openings 63 defined in the
upper surface part 61a is shown). The openings 63 are defined in
center regions of the upper surface part 61a and the lower surface
part 61b in the width direction W.
As shown in FIGS. 4 and 5, in the frame 61, rectangular openings
64, 64 are respectively formed in side surface parts 61c and 61d
perpendicular to the upper surface part 61a and the lower surface
part 61b. The openings 64 in the side surface part 61c and the
openings 64 in the side surface part 61d are formed
plane-symmetrically with respect to an imaginary plane located at
the center between the side surface part 61c and the side surface
part 61d. In the openings 64, rectangular base plates 65 are
fitted. In this embodiment, an arrangement in which the openings 64
are formed in the frame 61 to mount the base plates 65 in the
openings 64 is described by way of illustration. However, the
embodiment is not limited to the disclosed arrangement. For
example, the frame 61 may be integrally formed with the base plates
65 to eliminate the necessity of forming the openings 64 in the
frame 61.
The leaves 70 are formed in the shape of substantially rectangular
plates. The leaves 70 are formed of a material opaque to the
radiation beam S2, such as, for example, tungsten, or a tungsten
alloy.
As shown in FIG. 5, the leaves 70 are spaced apart from each other
and arranged in a line along the plate thickness direction T. The
leaves 70 constitute a leaf group 70G. The leaf group 70G in this
embodiment consists of thirty leaves 70, for example. As shown in
FIGS. 4 and 6, there are two leaf groups 70G formed as described
above, and the two leaf groups 70G constitute a pair positioned
within the leaf housing part 62 inside the frame 61 so as to be
opposed to each other across a center region in the width direction
W of the frame 61.
FIG. 7 is a perspective view showing a leaf 70 and a drive device
90 for driving the leaf 70.
As shown in FIGS. 6 and 7, the leaf 70 has a linear upper edge part
(an end surface) 70a and a linear lower edge part 70b which are
parallel to each other. As shown in FIG. 6, the upper edge part 70a
is opposed, at a distance, to the upper surface part 61a in the
leaf housing part 62. Similarly, in the leaf housing part 62, the
lower edge part 70b is opposed, at a distance, to the lower surface
part 61b.
The leaf 70 has a front edge part 70c which is outwardly curved in
the shape of an arc on a side of the leaf 70 facing the center
region in the width direction W of the frame 61 inside the leaf
housing part 62. Further, the leaf 70 has a rear edge part 70d
facing the outside of the frame 61 in the width direction W inside
the leaf housing part 62, and the rear edge part 70d is formed in
the shape of a line perpendicular to the upper edge part 70a and
the lower edge part 70b.
The pair of two leaf groups 70G, 70G, which are opposed to each
other across the center region along the width direction W within
the leaf housing part 62, are arranged in such a manner that the
front edge parts 70c of the leaves face a region defined between
the opening 63 in the upper surface part 61a of the frame 61 and
the opening 63 in the lower surface part 61b of the frame 61.
Each of the leaves 70 has slits 71 and 72 penetrating through the
plate thickness direction T of the leaves 70. Each of the slits 71
and 72 is continuously formed along a direction of connecting the
front edge part 70c to the rear edge part 70d in each of the leaves
70; i.e., the width direction W. The slits 71 and 72 are spaced
apart from each other and arranged side by side along a direction
of connecting the upper edge part 70a and the lower edge part 70b
in each of the leaves 70. The slits 71 and 72 are formed at
positions shifted from the front edge part 70c toward a rear edge
part 70d side so as not to be irradiated with the radiation beam S2
incident from the opening 63 in the upper surface part 61a of the
frame 61 into the leaf housing part 62 of the frame 61.
In each of the leaves 70, at least one of upper side edges 71a and
72a and lower side edges 71b and 72b of the slits 71 and 72 is
equipped with a rack gear 73 continuously extending along the width
direction W. Here, in the leaf group 70G, the rack gears 73 of
adjacent leaves 70 located side by side along the direction in
which the plurality of leaves 70 are arranged are mounted on
different side edges selected from among the upper side edges 71a,
72a and the lower side edges 71b, 72b of the slits 71 and 72. In
this way, pinion gears 96 engaging with the rack gears 73 of the
adjacent leaves 70 and 70 in the plate thickness direction T can be
prevented from interfering with each other.
The plurality of leaves 70 constituting each of the leaf groups 70G
are supported by the frame 61. The frame 61 supports the plurality
of leaves 70 in such a manner that the plurality of leaves are able
to advance and retreat along the width direction W perpendicular to
the plate thickness direction T. The frame 61 is equipped with
slide support members 66. The slide support members 66 are arranged
with a spacing along the width direction W on both an upper part
and a lower part of each of the leaf groups 70G. In this
embodiment, the upper part and the lower part in each of the leaf
groups G are respectively equipped with two of the slide support
members 66 for each of a center region side and an outer periphery
side of the frame 61 in the width direction W, and therefore, each
of the upper and lower parts includes a total of four of the slide
support members 66 to guide movement of the leaves 70.
As shown in FIGS. 5 and 6, each of the slide support members 66 has
a shaft 66a fixed to the frame 61 and a plurality of support
rollers 66b, each of which is rotatably supported on the shaft 66a.
The plurality of support rollers 66b are respectively disposed on
positions corresponding to the plurality of leaves 70 constituting
the leaf group 70G. The support rollers 66b are configured to be
rotatable along a direction in which the upper edge parts 70a and
the lower edge parts 70b of the leaves 70 are moved to advance.
As shown in FIG. 6, the upper edge part 70a and the lower edge part
70b of each of the leaves 70 are contacted by the support rollers
66b of the slide support members 66. At least two of the support
rollers 66 are provided for each of the upper edge part 70a and the
lower edge part 70b as the support rollers 66b making contact with
the upper edge part 70a or making contact with the lower edge part
70b.
That is, the leaves 70 are supported via the slide support members
66 by the frame 61 in a state where each of the leaves 70 is
independently advanceable or retreatable along the width direction
W.
Here, in the above-described leaf group 70G, the adjacent leaves 70
and 70 located side by side in the plate thickness direction T may
be designed to be respectively contacted by support rollers 66b
contained in different ones of the above-described slide support
members 66. This can prevent the support rollers 66b from
interfering with each other between the adjacent leaves 70, 70. In
this embodiment, the arrangement in which the leaves 70 are
supported by the slide support members 66 equipped with the
rotatable support rollers 66b has been described. However, the
embodiment is not limited to the arrangement. For example, the
leaves 70 may be slidably supported by means of slide support
members 66 that are not rotated. In this case, the slide support
members 66 may be provided, for example, with grooves in which the
upper edge parts 70a and the lower edge parts 70b of the leaves 70
are slidably retained.
The frame 61 has a stopper 68 for limiting an amount of movement of
each of the leaves 70 toward the rear edge part 70d side in the
width direction W.
FIG. 8 is a perspective view showing components of the drive device
90.
As shown in FIGS. 7 and 8, the drive device 90 is arranged for each
of the plurality of leaves 70 and associated therewith. The drive
device 90 includes a motor 91, a shaft 95, and a pinion gear
96.
The motor 91 is connected to a base end part of the shaft 95. The
motor 91 actuates the shaft 95 to be rotated about an axis
thereof.
Here, as shown in FIG. 5, the motors 91 are supported by the base
plates 65 mounted along the side surface parts 61c and 61d of the
frame 61.
The base plate 65 mounted on the side surface part 61c of the frame
61 supports the motors 91 in the drive devices 90 assigned to
drive, among the plurality of leaves 70 constituting the leaf group
70G, half of the leaves 70 located on a side closer to the side
surface part 61c. The base plate 65 mounted on the side surface
part 61d of the frame 61 supports the motors 91 in the drive
devices 90 assigned to drive, among the plurality of leaves 70
constituting the leaf group 70G, half of the leaves 70 located on a
side closer to the side surface part 61d.
As shown in FIG. 7, the shaft 95 extends along the plate thickness
direction T of the leaf 70. Further, as shown in FIGS. 6 and 7, the
shaft 95 is inserted into the slits 71 or 72 of the plurality of
leaves 70 in the leaf group 70G.
In addition, as shown in FIGS. 7 and 8, the pinion gear 96 is
attached to a tip end part of the shaft 95. The pinion gear 96 is
engaged with the rack gear 73 formed on any one of the upper side
edges 71a and 72b and the lower side edges 71b and 72b, which
constitute a part of the leaf 70, in the slits 71 and 72.
The drive device 90 further includes a rotary encoder 92 and a
cover 94.
The rotary encoder 92 measures a rotation quantity of the shaft 95
and outputs measured results to the controller 12.
The cover 94 is formed in the shape of a hollow pipe. The cover 94
is integrally formed with a housing 91a of the motor 91. A bearing
130 is attached to an end part of the cover on an opposite side
from the motor 91. In addition, the shaft 95 is inserted into the
cover 94. The shaft 95 is rotatably supported by the bearing 130.
In other words, the cover 94 supports the shaft 95 via the bearing
130 at a position spaced apart from the motor 91 along an extending
direction of the shaft 95. In this way, deformation of the shafts
95 caused by a self weight or other factors is prevented from
occurring, to ensure that the pinion gear 96 is reliably engaged
with teeth of the rack gear 73 even when the motor 91 is located
away from the leaf 70.
In the cover 94, a notch 94a is formed on a part of a
circumferential direction.
The notch 94a is provided to prevent the cover 94, to which the
notch 94a is provided, from interfering with leaves 70 located on a
motor 91 side of the cover 94 relative to the leaf 70 having the
rack gear 73 that is engaged with the pinion gear 96 of the shaft
95 inserted into the cover 94 to which the notch 94a is
provided.
In the drive device 90 as described above, the motor 91 is actuated
under control of the controller 12 to rotate the shaft 95. Rotation
of the shaft 95 causes the pinion gear 96 to be rotated together
with the shaft 95 whose rotating force is transferred to the rack
gear 73. Then, the leaf 70 equipped with the rack gear 73 is
shifted along an advancing or retreating direction which
corresponds to the width direction W.
In each of the two leaf groups 70G coupled as a pair, when the
leaves 70 constituting the leaf groups 70G are individually
advanced or retreated along the width direction W as described
above, the radiation beam S2 incident from the opening 63 on the
upper surface part 61a of the frame 61 is partially blocked by the
leaves 70 in the leaf groups 70G on both sides of the opening 63.
In other words, the multileaf collimator 60 functions to produce
the medical radiation beam Sr adjusted to have the shape
corresponding to a predetermined field of irradiation.
FIG. 9 is a diagram showing the shape of the leaves. FIG. 10 is an
enlarged view showing regions of two leaves in the leaf group
opposed to each other.
As shown in FIG. 9, each of the plurality of leaves 70 constituting
each of the leaf groups 70G has a protruded portion 75 and a
depressed portion 76.
The protruded portion 75 is formed on a surface 70f which is a
first side in the plate thickness direction T of the leaf 70. The
protruded portion 75 is continuously formed along the width
direction W. The protruded portion 75 has a pair of lateral
surfaces 75a and 75a and a top surface 75b. The lateral surfaces
75a are designed to be perpendicularly raised from the surface 70f.
The pair of lateral surfaces 75a are formed so as to be spaced
apart from each other in a vertical direction of connecting the
upper edge part 70a and the lower edge part 70b. The top surface
75b is formed in parallel with the surface 70f to connect the
lateral surfaces 75a, 75a.
In addition, a corner part 211 where the surface 70f intersects
with each of the lateral surfaces 75a of the protruded portion 75
is designed as a curved surface (a first curved surface) 220A
having a predetermined radius R1 of curvature.
The depressed portion 76 is formed on a surface 70g which is a
second side in the plate thickness direction T of the leaf 70. The
depressed portion 76 is continuously defined along the width
direction W. The depressed portion 76 has a pair of lateral
surfaces 76a and a bottom surface 76b. The lateral surfaces 76a are
extended perpendicular to the surface 70f toward a surface 70f
side. The pair of lateral surfaces 76a are formed so as to be
spaced apart from each other in the vertical direction of
connecting the upper edge part 70a and the lower edge part 70b. The
bottom surface 76b is formed in parallel with the surface 70f to
connect the pair of lateral surfaces 76a.
Further, a corner part 212 where the surface 70g intersects with
each of the lateral surfaces 76a is designed as a curved surface (a
second curved surface) 220B having a predetermined radius R2 of
curvature.
A center position between the pair of lateral surfaces 75a of the
protruded portion 75 and a center position between the pair of the
lateral surfaces 76a of the depressed portion 76 are defined to be
located substantially at the same position in the vertical
direction of the leaf 70. Further, a distance Z1 between the pair
of lateral surfaces 75a is defined to be smaller than a distance Z2
between the pair of lateral surfaces 76a.
In the leaf group 70G, the two leaves 70 (hereinafter, referred to
as a first leaf 70 and a second leaf 70, respectively) adjacent to
each other in the plate thickness direction T are positioned in
such a manner that the surface 70f of the first leaf 70 and the
surface 70g of the second leaf 70 are opposed to each other. In the
first leaf 70 and the second leaf 70 adjacent to each other in the
plate thickness direction T, the protruded portion 75 of the first
leaf 70 is accommodated in the depressed portion 76 of the second
leaf 70.
As shown in FIG. 10, the first leaf 70 and the second leaf 70
adjacent to each other are disposed side by side with a
predetermined gap g1 along the plate thickness direction T. In this
way, in-between the two leaves 70, a gap space 200 is created with
a bending section 210 which is bent in a cranked geometry between
the protruded portion 75 and the depressed portion 76.
The radiation beam S2 emitted from the radiation beam irradiation
device 24 travels into the gap space 200. In addition to traveling
along a straight line within the gap space 200, the radiation beam
S2 may propagate downward while being scattered by both lateral
surfaces in the gap space 200.
Therefore, in order to prevent leakage of the radiation beam S2
propagating through the gap space 200 downward of the leaf group
70G, the gap g1 in the plate thickness direction T between the two
leaves 70 and 70 is defined, for example, as follows:
0<g1.ltoreq.1.0 mm
Further, the radius R1 of curvature of the corner part 211 at the
intersection of the surface 70f and the lateral surface 75a of the
protruded portion 75 and the radius R2 of curvature of the corner
part 212 at the intersection of the lateral surface 76a and the
bottom surface 76b in the depressed portion 76 are defined as
follows: 0<R1.ltoreq.1.0 mm, and 0<R2.ltoreq.1.0 mm
Still further, a bending angle at each of the corner parts 211 and
212 is greater than or equal to 60.degree., and preferably equal to
approximately 90.degree. (for example, 85.degree.
.about.95.degree.).
Moreover, when the radius R1 of curvature of the corner part 211
and the radius R2 of curvature of the corner part 212 are
excessively great, there is a possibility that the radiation bean
S2 may leak through the gap space 200 and downwardly propagate to
regions below the leaf group 70G. With this in view, the radius R1
of curvature of the corner part 211 and the radius R2 of curvature
of the corner part 212 are preferably designed to be two times or
less of a level difference dimension t1 between the top surface 75b
of the protruded portion 75 and the surface 70f and two times or
less of a level difference dimension t2 between the bottom surface
76b of the depressed portion 76 and the surface 70g,
respectively.
Further, in the bending section 210, when any one of the radius R1
of curvature of the corner part 211, the radius R2 of curvature of
the corner part 212, the gap g1 in the plate thickness direction T
between the leaves 70 adjacent to each other along the plate
thickness direction T, and the gap g2 in the vertical direction
(the radiation direction of the radiation beam S2) between the
lateral surface 75a of the protruded portion 75 and the lateral
surface 76a of the depressed portion 76 is excessively great, there
is the possibility that the radiation beam S2 may leak through the
gap space 200.
Accordingly, the radii R1 and R2 of curvature and the gaps g1 and
g2 are specified, for example, as described below. In the
description below, it is assumed for the sake of simplicity that
the radius R1 of curvature=the radius R2 of curvature=the radius R
of curvature.
(a) When the gap g1.ltoreq.the gap g2, the radius R of curvature of
the corner part 211 and of the corner part 212 is defined to be
smaller than or equal to the gap g1 (R.ltoreq.g1).
In this case, the dose D of the radiation beam that is scattered
within the gap space 200 and leaked therefrom is defined as
follows: D.varies.A1.times.A2 (1) In the above expression, "A1"
represents an area of a scattering region U1 enclosed by the
surface 70f of the leaf 70, the lateral surface 75a of the
protruded portion 75, an extension line E1 from the surface 70g
opposed to the surface 70f across the gap space 200, and an
extension line E2 from the lateral surface 76a of the depressed
portion 76 opposed to the lateral surface 75a across the gap space
200. Further, "A2" represents an area of a scattering region U2
enclosed by the bottom surface 76b of the depressed portion 76 in
the leaf 70, the lateral surface 76a of the depressed portion 76 in
the leaf 70, an extension line E3 from the top surface 75b of the
protruded portion 75 opposed to the bottom surface 76b across the
gap space 200, and an extension line E4 from the lateral surface
75a of the protruded portion 75.
When the corner parts 211 and 212 are designed to maintain the
right angle rather than being formed as the curved surfaces 220A
and 220B having the radius R of curvature, the dose D is defined as
follows: D.varies.A1.times.A2.varies.(g1+g2).sup.2 (2) As opposed
to this, when the corner parts 211 and 212 are formed as the curved
surfaces 220A and 220B having the radius R of curvature, the dose D
is defined as follows:
D.varies.A1.times.A2.varies.(g1+g2-2R.times.(1-.pi./4)).sup.2
(3)
This means that the dose D of the leaked radiation beam can be
reduced by forming the corner parts 211 and 212 in the shape of the
curved surfaces 220A and 220B having the radius R of curvature.
(b) In a case of g2.ltoreq.g1, the radius R of curvature of the
corner parts 211 and 212 is defined to be smaller than or equal to
the gap g2 (R.ltoreq.g2).
When the corner parts 211 and 212 are designed to maintain the
right angle rather than being formed as the curved surfaces 220A
and 220B having the radius R of curvature, the dose D is defined as
follows: D.varies.A1.times.A2.varies.(g1+g2).sup.2 (2) As opposed
to this, when the corner parts 211 and 212 are formed as the curved
surfaces 220 A and 220B having the radius R of curvature, the dose
D is defined as follows:
D.varies.A1.times.A2.varies.(g1+g2-2R.times.(1-.pi./4)).sup.2
(3)
This means that the dose D of the leaked radiation beam can be
reduced by forming the corner parts 211 and 212 in the shape of the
curved surfaces 220A and 220B having the radius R of curvature.
(c) In a case of g1.ltoreq.g2, the radius R of curvature of the
corner parts 211 and 212 is defined to have a relationship of
g1.ltoreq.R.ltoreq.g2.
When the corner parts 211 and 212 are designed to maintain the
right angle rather than being formed as the curved surfaces 220A
and 220B having the radius R of curvature, the dose D is defined as
follows: D.varies.A1.times.A2.varies.(g1+g2).sup.2 (2) As opposed
to this, when the corner parts 211 and 212 are formed as the curved
surfaces 220A and 220B having the radius R of curvature, the dose D
is defined as follows:
D.varies.A1.times.A2.varies.(g2-R+Rcos.sup.-1((R-g1)/R)).sup.2
(4)
This means that the dose D of the leaked radiation beam can be
reduced by forming the corner parts 211 and 212 in the shape of the
curved surfaces 220A and 220B having the radius R of curvature.
(d) In a case of g2.ltoreq.g1, the radius R of curvature of the
corner parts 211 and 212 is defined to have a relationship of
g2.ltoreq.R.ltoreq.g1.
When the corner parts 211 and 212 are designed to maintain the
right angle rather than being formed as the curved surfaces 220A
and 220B having the radius R of curvature, the dose D is defined as
follows: D.varies.A1.times.A2.varies.(g1+g2).sup.2 (2) As opposed
to this, when the corner parts 211 and 212 are formed as the curved
surfaces 220A and 220B having the radius R of curvature, the dose D
is defined as follows:
D.varies.A1.times.A2.varies.(g1-R+Rcos.sup.-1((R-g2)/R)).sup.2
(5)
This means that the dose D of the leaked radiation beam can be
reduced by forming the corner parts 211 and 212 in the shape of the
curved surfaces 220A and 220B having the radius R of curvature.
(e) In a case of g1.ltoreq.g2, the curved surfaces 220A and 220B of
the corner parts 211 and 212 are designed to be respectively
located outside of circles drawn with a radius r in the range of
0<r<g1 around apexes 215 which are inwardly located in
bending directions and opposed to the corner parts 211 and 212. In
this way, the dose of the scattered beam can be reduced.
(f) In a case of g2.ltoreq.g1, the curved surfaces 220A and 220B of
the corner parts 211 and 212 are designed to be respectively
located outside of circles drawn with a radius r in the range of
0<r<g2 around the apexes 215 which are inwardly located in
the bending directions and opposed to the corner parts 211 and 212.
In this way, the dose of the scattered beam can be reduced.
In the radiation treatment system 10 as described above, a
treatment is performed as described below.
First, a user secures a patient B on the couch 28 of the radiation
treatment apparatus 20 in a posture indicated in a treatment plan
that is input into the treatment planning apparatus 11.
The controller 12 activates the rotation drive mechanism (not shown
in the drawing) and a gantry drive device (not shown). More
specifically, the controller 12 causes the ring frame 21 and the
travelling gantry 22 to rotate around the center axes C1 and C2 for
moving the radiation beam irradiation device 24 to irradiate a
position of an affected site in the patient B with the medical
radiation beam Sr at an irradiation angle indicated in the
treatment plan. Further, the controller 12 causes each of the drive
devices 90 to advance or retreat corresponding one of the leaves 70
for changing the shape of a field irradiated with the medial
radiation beam Sr while being regulated by the multileaf collimator
60 into the shape indicated in the treatment plan input into the
treatment planning apparatus 11.
Then, the controller 12 uses the radiation beam irradiation device
24 to irradiate the affected site of the patient B with the medial
radiation beam Sr at the dose indicated in the treatment plan input
into the treatment planning apparatus 11.
According to the multileaf collimator 60 in the above-described
embodiment, because the curved surfaces 220A and 220B are
respectively formed between the surface 70f of the leaf 70 and the
lateral surface 75a of the protruded portion 75 and between the
surface 70g and the lateral surface 76a of the depressed portion
76, stress is not easily concentrated on any portion of the leaf
70. Therefore, cracking and breakage can be prevented from
occurring while reducing leakage of the radiation beam S2.
In addition, leakage of the radiation beam S2 can be reliably
minimized by appropriately setting the radii R1 and R2 of curvature
of the curved surfaces 220A and 220B based on the gasp g1 and g2
between the two leaves 70 arranged side by side in the plate
thickness direction T.
Modification Example of Embodiment
Although the corner part 211 at the intersection of the surface 70f
of the leaf 70 and each of the lateral surfaces 75a of the
protruded portion 75 and the corner part 212 at the intersection of
the surface 70g and the lateral surface 76a are designed as the
curved surfaces 220A and 220B, the embodiment is not limited to
such geometry.
FIG. 11 is a diagram showing a modification example of the leaf
illustrated in the above embodiment.
As shown in FIG. 11, curved surfaces 220C and 220D having a
predetermined radius of curvature may be formed in the leaf 70
between the lateral surface 75a and the top surface 75b of the leaf
70 and between the lateral surface 76a of the depressed portion 76
and the surface 70g of the leaf 70.
Other Embodiments
The present invention is not limited to the above-described
embodiment, and may be modified in design without departing from
the gist of the invention.
INDUSTRIAL APPLICABILITY
When the first curved surface is formed between the first side
surface of the leaf and the lateral surface of the protruded part
and the second curved surface is formed between the second side
surface of the leaf and the lateral surface of the depressed
portion, leakage of the radiation beam can be minimized while
preventing cracking and breakage from occurring in the leaf.
REFERENCE SIGNS LIST
10 radiation treatment system 11 treatment planning apparatus 12
controller 20 radiation treatment apparatus 21 ring frame 21a lower
end part 22 travelling gantry 22a inner circumferential surface 23
sensor array 24 radiation beam irradiation device 25 rotating shaft
26A, 26B source 27A, 27B sensor array 28 couch 28a upper surface 29
couch actuator 51 electron beam accelerator 52 X-ray target 53
primary collimator 53h through hole 54 flattening filter 54a
protrusion 55 secondary collimator 55h through hole 60 multileaf
collimator 61 frame 61a upper surface part 61b lower surface part
61c, 61d side surface part 62 leaf housing part 63 opening 64
opening 65 base plate 66 slide support member 66a shaft 66b support
roller 68 stopper 70 leaf 70G leaf group 70a upper edge part 70b
lower edge part 70c front edge part 70d rear edge part 70f surface
70g surface 71, 72 slit 71a, 72a upper side edge 71b lower side
edge 73 rack gear 75 protruded portion 75a lateral surface 75b top
surface 76 depressed portion 76a lateral surface 76b bottom surface
90 drive device 91 motor 91a housing 92 rotary encoder 94 cover 95
shaft 96 pinion gear 101 X-ray 130 bearing 200 gap space 210
bending section 211 corner part 212 corner part 215 apex 220A
curved surface (first curved surface) 220B curved surface (second
curved surface) 220C curved surface 220D curved surface B patient
C0 isocenter C1 center axis C2 center axis E1, E2, E3, E4 extension
line g1 gap g2 gap P circle Q circle R radius of curvature r radius
R1 radius of curvature R2 radius of curvature S0 electron beam S1
radiation beam S2 radiation beam Sr medical radiation beam T plate
thickness direction t1 level difference dimension t2 level
difference dimension U1 scattering region U2 scattering region W
width direction Z1 distance Z2 distance .theta.1 intersection angle
.theta.2 intersection angle
* * * * *